[clang-format] Allow breaking before bit-field colons (#153529)

Fixes #153448

Author: owenca

clang/lib/Format/TokenAnnotator.cpp

@@ -6272,7 +6272,8 @@ bool TokenAnnotator::canBreakBefore(const AnnotatedLine &Line,
   }
 
   if (Right.is(tok::colon) &&
-      !Right.isOneOf(TT_CtorInitializerColon, TT_InlineASMColon)) {
+      !Right.isOneOf(TT_CtorInitializerColon, TT_InlineASMColon,
+                     TT_BitFieldColon)) {
     return false;
   }
   if (Left.is(tok::colon) && Left.isOneOf(TT_DictLiteral, TT_ObjCMethodExpr)) {

clang/unittests/Format/FormatTest.cpp

@@ -4050,6 +4050,10 @@ TEST_F(FormatTest, FormatsBitfields) {
                "  uchar : 8;\n"
                "  uchar other;\n"
                "};");
+  verifyFormat("struct foo {\n"
+               "  uint8_t i_am_a_bit_field_this_long\n"
+               "      : struct_with_constexpr::i_am_a_constexpr_lengthhhhh;\n"
+               "};");
   FormatStyle Style = getLLVMStyle();
   Style.BitFieldColonSpacing = FormatStyle::BFCS_None;
   verifyFormat("struct Bitfields {\n"